Development of the intestinal SGLT1 transporter in rats

Glucose absorption from the small intestine is largely mediated via the sod ium-coupled glucose transporter (SGLT1). The goal of this study was to inve stigate the ontogenesis of the SGLT1, using the rat as an animal model at t hree stages of development: during lactation, at weaning, and at physiologi c maturity. The techniques involved upper small intestinal perfusions with solutions containing 200 mM glucose and 50 mM NaCl, with or without 1 mM ph loridzin (Phl), as an inhibitor of SGLT1. Molecular expression of the SGLT1 was also investigated via Western blot analysis from intestinal specimens of the three growth periods. Glucose absorption in weanling rats, in the ab sence of Phl, was several times higher than in sucklings and approximately double that of mature animals, and the effects of Phl were the greatest in weanlings. Furthermore, the physiologic data correlate to the molecular ana lysis of the SGLT1 which showed an increase in expression of the SGLT1 in b oth the weanlings and the adults compared to the sucklings. At all three st ages of development Phl abolished Na absorption, and in sucklings there was a net outflow of Na. Due to the coupling between Na and water transport, n et water absorption and the influx/efflux ratio, a more sensitive indicator of changes in unidirectional fluid movement, were similarly affected by Ph l at the three stages of development. Net water absorption was highest in w eanling animals. These findings are consistent with an early development of SGLT1 in rat small intestine and an apparent burst of activity at weaning. Less than complete maturity of other absorptive mechansims is occurring at this time. (C) 2000 Academic Press.